An organic compound with molecular formula ${\mathrm{C}}_3{\mathrm{H}}_5\mathrm{N}$ on hydrolysis gives an acid which reduces the Fehling solution. The compound can be

Fehling test is used to differentiate between the aldehyde and ketone functional groups.

Positive Fehling test is given by aldehydes, alpha-hydroxy ketones and formic acid.

Now,

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{NC}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{NH}}_2+\mathrm{HCOOH}$

The formic acid formed on the hydrolysis of ethanenitrile gives a positive Fehling test.

Hence, option (B) is correct.